1. Field of the Invention
The present invention relates to an optical fiber communication cable in which the optical fibers and/or ribbons are bound and assorted into groups by using water swellable material having indicia (e.g., different colors, color strips/prints and/or simply mono-color strips/prints) to distinguish the groups.
2. Discussion of Related Art
Conventional optical fiber cables include optical fibers that are sometimes grouped together in sets (with each set having one or more, e.g., twelve, optical fibers) with each fiber in a particular set having a unique color. Thus, within a single set, the optical fibers are coated with distinctly different colors. These distinct colors are repetitively used for each set, so that if there are three sets of optical fibers, the optical fiber cable will have, e.g., three red optical fibers, three green optical fibers, etc. In order to distinguish between optical fibers having the same color, it is necessary to color code each set of optical fibers. To accomplish this, the optical fiber sets are wrapped by different colored binder threads such that, e.g., a first set is held together by a blue binder thread, a second set is held together by a yellow binder thread and a third set is held together by an orange binder thread, and so on and so forth. In this way, one can identify the optical fibers by the specific color of the optical fiber and the associated color of the optical fiber set, e.g. red optical fiber of the blue optical fiber set or the green optical fiber of the yellow optical fiber set. This arrangement is illustrated in FIGS. 1 and 2 showing an optical fiber cable 10 having four optical fiber sets 12 respectively held together by colored binder threads 14. The optical fiber sets 12 are enclosed in a buffer tube 16 and a water block gel 18 is filled in the space defined between the optical fibers. The buffer tubes are then encapsulated by an outer sheath 20 having rigid strengthening members 22.
Although not shown, it is also known to wrap the optical fiber ribbons or tubes with a water swellable material to prevent moisture from adversely affecting the optical fiber, as disclosed in U.S. Pat. No. 5,384,880.
The problem with this arrangement is that with higher and higher buffering process speeds, the gel feeding could become the bottleneck of the process. The higher buffering line speed may induce problems due to the gel not being able to fill the buffer tube, which will result in the formation of air bubbles or voids in the gel thus inhibiting the water block capacity of the gel. Also, an excessively high gel feeding speed imposes high shear stress on the gel which can potentially decompose the gel. In turn, the decomposed gel may yield compound flow failure or water penetration failure issues in the cable. The gel properties effected by the high shear stress can cause process instability and make the overall process of manufacturing the optical cable complex.
More importantly, due to the presence of the water block gel, it is inconvenient and messy to access the fibers in field applications and the exposed gel may also become a source of environmental hazard.